Mansell shadowed race winner Luke Browning for much of the race after rising from eighth on the grid.
He climbed up the order quickly in the opening laps to sit second after six of the 22 scheduled laps.
Tucked up under Browning’s rear wing, there Mansell stayed, unable to find a way through.
“We played the offensive, for sure,” the 19-year-old told Speedcafe.
“I made a lot of clean and decisive moves very, very early in the race.
“I was a bit worried that maybe I burnet through the tyres, but seemed to manage quite nicely – just being in the DRS, they sort of came back a bit.”
Having reeled in the 1.3-second advantage Browning had built in the early laps, Mansell remained glued to the gearbox of the Williams Academy driver from that point on.
“We were just consolidating,” Mansell said.
“We were basically not pushing, trying to save the tyres and obviously see what we can do at the end of the race.
“I really wanted to go for it, but the team said just sit tight, just wait, and that’s what I did.”
Mansell is in his second season of Formula 3, having competed with Spanish operation Campos Racing last year. He’s switched to French team ART Grand Prix for 2024.
That saw him qualify eighth on Thursday, translating to fourth on the grid for the reverse-top-12 Sprint race on Friday.
However, a set-up choice meant he slipped down the order and prompted a change for Saturday’s encounter.
The resulting conversation proved decisive and transformed Mansell’s weekend.
“We made a few adjustments to the car, considering it was really, really different than today’s performance,” the Novacastrian admitted.
“The whole dynamic; we went the wrong direction and now we went to a different direction. Through myself and my engineer, we came to that conclusion. We were both on the same page.
“As soon as the [Sprint] race finished, we were like ‘right, we’ve got to go opposite to where we went to’.
“I’m really happy that we went that way.”
The result has left Mansell third behind Browning and Tim Tramnitz in the F3 championships standings after the first of 10 rounds, the next of which is in Melbourne alongside the Australian Grand Prix next month.